Such a composite matrix has been disclosed in the U.S. Pat. No. 5,330,353, and clinical tests have shown that the metallic part of the matrix makes easier the introduction of the matrix between two teeth, whereas the synthetics part is necessary for the exposure of teeth fillings of polymerizable synthetic material to light. In the mentioned U.S. patent, relatively few indications can be found referring to the manufacture of such a composite matrix; it is only said that the metal foil is joined to the synthetics foil by microetching and heat sealing.